Improve UX: autofill cfg param with proper accel type, printout cfg params

modules/gapi/include/opencv2/gapi/streaming/onevpl/cfg_params.hpp

@@ -185,6 +185,8 @@ struct GAPI_EXPORTS CfgParam {
     const name_t& get_name() const;
     const value_t& get_value() const;
     bool is_major() const;
+    std::string to_string() const;
+
     bool operator==(const CfgParam& rhs) const;
     bool operator< (const CfgParam& rhs) const;
     bool operator!=(const CfgParam& rhs) const;

modules/gapi/samples/onevpl_infer_single_roi.cpp

@@ -59,7 +59,7 @@ const std::string keys =
     "{ vpp_frames_pool_size         | 0                                         | OneVPL source applies this parameter as preallocated frames pool size for VPP preprocessing results}"
     "{ roi                          | -1,-1,-1,-1                               | Region of interest (ROI) to use for inference. Identified automatically when not set }"
     "{ source_device                | CPU                                       | choose device for decoding }"
-    "{ preproc_device               | CPU                                       | choose device for preprocessing }";
+    "{ preproc_device               |                                           | choose device for preprocessing }";
 
 
 namespace {
@@ -609,11 +609,6 @@ int main(int argc, char *argv[]) {
         if (is_gpu(source_device)) {
             std::cout << "enforce VPL Source deconding on device: " << source_device << std::endl;
             // use special 'Device' constructor for `onevpl::GSource`
-            // put accel type description for VPL source
-            source_cfgs.push_back(cfg::create_from_string(
-                                        "mfxImplDescription.AccelerationMode"
-                                        ":"
-                                        "MFX_ACCEL_MODE_VIA_D3D11"));
             cap = cv::gapi::wip::make_onevpl_src(file_path, source_cfgs,
                                                  gpu_accel_device.value(),
                                                  gpu_accel_ctx.value());

modules/gapi/src/streaming/onevpl/accelerators/accel_policy_va_api.cpp

@@ -28,6 +28,7 @@ VPLVAAPIAccelerationPolicy::VPLVAAPIAccelerationPolicy(device_selector_ptr_t sel
     VPLAccelerationPolicy(selector),
     cpu_dispatcher(new VPLCPUAccelerationPolicy(selector)),
     va_handle() {
+    GAPI_LOG_INFO(nullptr, "created - TODO dispatchered on CPU acceleration");
 #if defined(HAVE_VA) || defined(HAVE_VA_INTEL)
     // setup VAAPI device
     IDeviceSelector::DeviceScoreTable devices = get_device_selector()->select_devices();

modules/gapi/src/streaming/onevpl/cfg_param_device_selector.cpp

@@ -65,7 +65,7 @@ private:
 struct Aux {};
 #endif
 
-static std::vector<CfgParam> insertCfgparam(std::vector<CfgParam> &&param_array, AccelType type) {
+std::vector<CfgParam> update_param_with_accel_type(std::vector<CfgParam> &&param_array, AccelType type) {
     switch (type) {
         case AccelType::HOST:
             break;

modules/gapi/src/streaming/onevpl/cfg_param_device_selector.hpp

@@ -21,6 +21,8 @@ namespace wip {
 namespace onevpl {
 
 class Aux;
+std::vector<CfgParam> update_param_with_accel_type(std::vector<CfgParam> &&param_array, AccelType type);
+
 struct GAPI_EXPORTS CfgParamDeviceSelector final: public IDeviceSelector {
     CfgParamDeviceSelector(const CfgParams& params = {});
     CfgParamDeviceSelector(Device::Ptr device_ptr,

modules/gapi/src/streaming/onevpl/cfg_params.cpp

@@ -4,6 +4,7 @@
 //
 // Copyright (C) 2021 Intel Corporation
 
+#include <sstream>
 #include <opencv2/gapi/util/throw.hpp>
 
 #include <opencv2/gapi/streaming/onevpl/cfg_params.hpp>
@@ -25,6 +26,15 @@ struct variant_comparator : cv::util::static_visitor<bool, variant_comparator> {
 private:
     const CfgParam::value_t& rhs;
 };
+
+struct variant_stringifier : cv::util::static_visitor<std::string, variant_stringifier> {
+    template<typename ValueType>
+    std::string visit(const ValueType& lhs) const {
+        std::stringstream ss;
+        ss << lhs;
+        return ss.str();
+    }
+};
 } // namespace util
 
 struct CfgParam::Priv {
@@ -228,6 +238,11 @@ bool CfgParam::is_major() const {
     return m_priv->is_major_impl();
 }
 
+std::string CfgParam::to_string() const {
+    return get_name() + ":" + cv::util::visit(util::variant_stringifier{},
+                                              get_value());
+}
+
 bool CfgParam::operator< (const CfgParam& rhs) const {
     return *m_priv < *rhs.m_priv;
 }

modules/gapi/src/streaming/onevpl/engine/decode/decode_engine_legacy.cpp

@@ -186,6 +186,9 @@ VPLLegacyDecodeEngine::SessionParam VPLLegacyDecodeEngine::prepare_session_param
         mfxDecParams.IOPattern = MFX_IOPATTERN_OUT_VIDEO_MEMORY;
     } else if (accel_type == AccelType::HOST) {
         mfxDecParams.IOPattern = MFX_IOPATTERN_OUT_SYSTEM_MEMORY;
+    } else if (accel_type == AccelType::VAAPI) {
+        // TODO make proper direction
+        mfxDecParams.IOPattern = MFX_IOPATTERN_OUT_SYSTEM_MEMORY;
     } else {
         GAPI_Assert(false && "unsupported AccelType from device selector");
     }

modules/gapi/src/streaming/onevpl/source.cpp

@@ -36,7 +36,7 @@ GSource::GSource(const std::string& filePath,
 GSource::GSource(const std::string& filePath,
                  const CfgParams& cfg_params,
                  const Device &device, const Context &ctx) :
-    GSource(filePath, cfg_params,
+    GSource(filePath, update_param_with_accel_type(CfgParams{cfg_params}, device.get_type()),
             std::make_shared<CfgParamDeviceSelector>(device, ctx, cfg_params)) {
 }
 

modules/gapi/src/streaming/onevpl/source_priv.cpp

@@ -94,12 +94,12 @@ GSource::Priv::Priv(std::shared_ptr<IDataProvider> provider,
          GAPI_Assert(cfg_inst && "MFXCreateConfig failed");
 
         if (!cfg_param_it->is_major()) {
-            GAPI_LOG_DEBUG(nullptr, "Skip not major param: " << cfg_param_it->get_name());
+            GAPI_LOG_DEBUG(nullptr, "Skip not major param: " << cfg_param_it->to_string());
             ++cfg_param_it;
             continue;
         }
 
-        GAPI_LOG_DEBUG(nullptr, "Apply major param: " << cfg_param_it->get_name());
+        GAPI_LOG_DEBUG(nullptr, "Apply major param: " << cfg_param_it->to_string());
         mfxVariant mfx_param = cfg_param_to_mfx_variant(*cfg_param_it);
         mfxStatus sts = MFXSetConfigFilterProperty(cfg_inst,
                                                    (mfxU8 *)cfg_param_it->get_name().c_str(),
@@ -189,8 +189,14 @@ GSource::Priv::Priv(std::shared_ptr<IDataProvider> provider,
 
     // Extract the most suitable VPL implementation by max score
     auto max_match_it = matches_count.rbegin();
-    GAPI_Assert(max_match_it != matches_count.rend() &&
+    if (max_match_it == matches_count.rend()) {
-                "Cannot find matched MFX implementation for requested configuration");
+        std::stringstream ss;
+        for (const auto &p : cfg_params) {
+            ss << p.to_string() << std::endl;
+        }
+        GAPI_LOG_WARNING(nullptr, "No one suitable MFX implementation is found, requested params:\n" << ss.str());
+        throw std::runtime_error("Cannot find any suitable MFX implementation for requested configuration");
+    }
 
     // TODO impl_number is global for now
     impl_number = max_match_it->second;